The present invention is directed to a process of forming openings in construction material, such as concrete, rock or the like, containing steel reinforcing members and using hand-held drilling devices with drilling, milling or chisel bits for forming the opening.
To form openings, such as bores, grooves or the like, at the present time, apart from so-called wall milling devices, principally drilling devices or chipping hammers are used. Such devices operate on an electropneumatic system with a considerably higher material removal performance as compared to impact or percussion drilling devices which have been used in the past.
A problem which has existed in the past is that during the drilling operation the drill bit might contact a steel reinforcing member, since the member is not visible from the exterior of the material being drilled. If such contact occurs, the bit is very rapidly damaged in view of the impact energy when the bit contacts the reinforcing member and after a short time the bit becomes unusable.
Metal detectors are known for locating steel reinforcing members within the construction material. Such devices, however, are very inaccurate and from a practical point of view are suitable only for the detection of reinforcing members located directly below the surface of the construction material. In addition, such detectors are very delicate and are not suitable for the rough handling experienced at construction sites.
There are other expensive means for determining the location of the reinforcing members, such as X-ray technology and ultrasonic procedures or the like, however, they are not utilized because of practical and economic considerations.